Applying scrim tape correctly over GIB joins is one of the most important steps in achieving a smooth, crack-free stopped finish. Done properly, it reinforces the join and prevents cracking as the building moves over time. Rush it or skip it, and you'll likely see cracks reappear through your paint within a season or two.
What Is Scrim Tape and Why Does It Matter?
Scrim tape (also called fibreglass mesh tape or jointing tape) is a self-adhesive, open-weave fibreglass mesh used to reinforce joins between plasterboard sheets before stopping compound is applied. It bridges the gap between sheets and gives the stopping compound something to key into, dramatically reducing the risk of cracking at joins.
For standard interior GIB plasterboard installations, scrim tape is the most common choice for flat joins. GIB's technical literature also specifies paper tape for certain applications (such as internal corners and some butt joins), so it's worth checking the GIB Stopping Guide for your specific situation.
Tools and Materials You'll Need
- Self-adhesive fibreglass scrim tape (typically 50–100 mm wide)
- GIB Tradeset or similar stopping compound (base coat)
- 150–200 mm broad knife or stopping knife
- 250–300 mm finishing knife (for later coats)
- Sanding pole and abrasive mesh or sandpaper
- Corner bead (for external corners — scrim tape is not used here)
- Clean bucket and mixing paddle (if using powder compound)
You can find scrim tape and stopping compounds at Bunnings, Mitre 10, or PlaceMakers.
Step-by-Step: Applying Scrim Tape Over GIB Joins
1. Prepare the Surface
Before you touch the tape, make sure all GIB sheets are correctly fixed — screws or nails should be driven just below the surface without breaking the paper face. Remove any dust, loose paper, or debris from the joins. If any screw heads are proud, drive them in slightly further.
2. Check the Join Type
Not all joins are the same:
- Recessed (tapered) joins — where the factory-tapered edges of two sheets meet. These are the easiest to tape and stop because the recess gives you room to build up compound flush with the board face.
- Butt joins — where two cut (non-tapered) edges meet. These are harder to finish invisibly and may require a wider feathering area.
- Internal corners — GIB recommends paper tape folded into the corner rather than scrim tape for these, as scrim can be harder to finish neatly.
- External corners — use metal or plastic corner bead, not tape.
3. Apply the Scrim Tape
Scrim tape is self-adhesive, so no pre-coating is needed (unlike paper tape, which requires a wet bed of compound first).
- Cut a length of scrim tape to match the join — run it the full length without joins in the tape itself where possible.
- Centre the tape over the join and press it firmly along the length, smoothing out any bubbles or wrinkles as you go. The tape should sit flat and adhere fully to both sheets.
- For long runs, work in manageable sections of 1–1.5 m at a time to keep the tape straight.
- At internal corners, fold the tape neatly into the corner and press both sides flat.
4. Apply the First Coat of Stopping Compound
Once the tape is in place, mix your base coat compound to a smooth, lump-free consistency (similar to thick peanut butter). Using your broad knife:
- Load the knife with compound and apply a firm, even coat directly over the tape, pressing the compound into the mesh.
- Feather the edges out 100–150 mm either side of the tape on recessed joins, wider on butt joins.
- Work the knife at a low angle to push compound into the mesh weave — you should see the tape pattern through the compound at this stage, which is normal.
- Remove excess compound with a clean stroke. Don't try to make it perfect at this stage — that's what subsequent coats are for.
- Allow to dry fully (typically overnight, depending on humidity and temperature).
5. Sand and Apply Further Coats
Stopping is a multi-coat process — typically three coats for a Level 4 finish (standard for painted walls):
| Coat | Purpose | Width |
|---|---|---|
| First (base) coat | Embed tape, fill join | ~200 mm |
| Second coat | Build up and level | ~300 mm |
| Third (finish) coat | Final levelling, feathering | ~400 mm+ |
Lightly sand between coats once fully dry. The finished surface should be flat with no visible tape edges or ridges.
Common Mistakes to Avoid
- Skipping the tape entirely — compound alone will crack at joins over time
- Bubbles or lifted tape edges — press tape down firmly before stopping
- Applying compound too thick in one coat — thin coats dry more evenly and are less prone to cracking
- Stopping over damp compound — always let each coat dry completely
- Using scrim tape on internal corners — use paper tape or a purpose-made corner tape instead
When to Call a Professional
Stopping to a high-quality finish is a skilled trade. If you're working on a large area, a new build, or need a Level 5 finish (for gloss paints or critical lighting), it's well worth engaging a qualified plasterer. Poor stopping is very hard to hide once painted. You can find experienced local plasterers on tradedirectory.co.nz.
Note that stopping itself is not restricted work under the NZ Building Code, but if your GIB installation is part of a fire-rated or bracing system, ensure the work meets the relevant MBIE Building Performance requirements and check with your local council whether a building consent is needed.
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